This flex-coupler for exhaust systems is 2.5” dia. ID, and 6” long. If features stainless-steel braiding, and requires welding to install. It is easy to install in a 2.5” exhaust system and is highly recommended when using the ORS 3.4L Conversion Crossover Pipe, or exhaust headers. It is meant to be installed downstream of the exhaust collector, just before or after the catalytic converter.